1. Field of the Invention
The present invention relates to a shutter device of a camera comprising a traveling state detection device.
2. Background of Related Art
A known mechanism around the light blocking blade of a focal plane shutter of a camera has a structure as shown in FIG. 4, an exploded perspective side view of the shutter mechanism. The substrate 1 and the cover plate 2 are positioned substantially parallel with holes 1b, 1c, 1d and 1e aligned with holes 2b, 2c, 2d, and 2e, respectively and connected by rods 7, 8, and 9. Moreover, exposure openings 1a and 2a are provided on the substrate 1 and the cover plate 2, respectively. Between the substrate 1 and the cover plate 2, four diaphragm plates, 3, 4, 5, and 6, are mounted 2 so that the rods 7 and 8 are inserted into the holes 3a, 3b, 4b, 4c, 5b, 5c, 6a, and 6b as shown in FIG. 4. In addition, the diaphragm plates 4 and 5, as with the substrate 1 and the cover plate 2, include exposure openings 4a and 5a respectively. As known, a front curtain 11 and a rear curtain 12 are positioned between the diaphragm plates 5 and 6, and between diaphragm plates 3 and 4, respectively. The front curtain 11 and the rear curtain 12 are between openings 1a, 2a, 4a, and 5a that are opened and closed by a drive mechanism (not shown) to provide the necessary exposure to a light sensitive film or the like (not shown).
With this type of shutter, exposure to the film image plane commences as the front curtain 11 is removed from the image plane by the depression of the shutter button in a known manner. After a specified time elapses, the rear curtain 12 is operated to cover the film image plane. The travel motion of each curtain is caused by spring force applied mechanically, the commencement of the travel motion being operated by releasing an engagement stop of each curtain.
Previously, these operations have been primarily controlled entirely mechanically. However, in recent years electrical control has also been used. To move the front and rear curtains themselves, a spring force is used as has been done in the past, with the commencement of the movement being controlled based on turning on the electricity to an electromagnet to release engagement with the curtains.
On the other hand, along with faster shutter speeds such as 1/8000 of a second, in recent years use of strobe lights has been substantial, and making the synchronized speed of the strobe light high has become important for high speed photography in a bright environment.
In order to accomplish this objective, the traveling speed of each curtain needs to be increased substantially by increasing the level of the spring force while the width of the slit between the front and the rear curtain is controlled to be narrow. Because of this, at the time of a high-speed exposure of less than 1/8000 of a second, even though the timing of turning on electricity to the electromagnet is accurately controlled, the desired shutter speed may not be obtained due to the actions of release of engagement stopping for the electromagnet with which a mechanical traveling system which includes the spring is endowed. Furthermore, to determine lack of desired operation before film development, an operation state detection device in the shutter for detecting the state of the operation immediately after shooting has been proposed.
Normally with such an operation state detection device, detection beams are emitted from an emitter by a positioning detection element including an emitter and a light receiver, with a reflecting mirror facing the emitter light detector, the beam reflecting off the reflection mirror to the light receiver; the state of opening and closing of the front curtain 11 and the rear curtain 12 being detected by causing the travel of the front curtain 11 and the rear curtain 12 during that time. However, because of the presence of the diaphragm plates 3-6 around the front curtain 11 and the rear curtain 12 as described previously, simply installing an operation state detection device in the shutter creates a problem in which the detection beam is blocked out by the diaphragm plates(s).